Someone is always listening. Especially on the train.

That’s the lesson for Pillsbury Winthrop Shaw Pittman, which said Thursday it will conduct layoffs after the legal blog Above the Law reported an anonymous tipster’s detailed description of a loud cell phone conversation in a public place between two senior managers regarding the reductions.

“We apologize for the unfortunate manner in which our deliberations about reductions have become public,” Pillsbury said in a statement issued Thursday morning. “It is an unfortunate fact in today’s economy that no business or law firm can rule out adjustments to their overall workforce levels. This includes Pillsbury, and among other cost-cutting measures, we will be implementing reductions to assure that our resources are aligned with our business needs.”

The call apparently took place between Robert Robbins, head of the corporate and securities practice, and COO Richard Donaldson. Robbins reportedly named out loud at least some of the 15 to 20 attorneys who the firm was talking about laying off in four offices by the end of March. The conversation apparently took place on an Amtrak train between Washington, D.C., and New York.

“I, along with all of the other passengers, were sitting quietly when the man directly behind me decided to make a phone call using his Bluetooth. He was talking so loudly that I think most people in the car were able to hear him,” the tipster apparently told ATL.

“His conversation, though he stressed how necessary it was to be kept secret [ah, the irony], detailed the current plans of Pillsbury to lay off somewhere in the range of 15-20 attorneys from four offices by the end of March, including a few senior associates with low billable hours and two or three first-year associates,” the tipster continued.

Firms are increasingly wary of the instant flow of information made possible by blogs, which are more receptive to anonymous information than traditional media.

“Most firms assume that any communications they make internally, particular to associates, will get on a blog, and they try to tailor those communications accordingly,” said Newport Beach, Calif.-based consultant Peter Zeughauser.

Comments posted below blog stories often reveal confidential information as well. By the end of the day, more than 300 comments were logged on the ATL story, with one poster claiming to be a Pillsbury associate who had been told to leave by the end of March and wasn’t offered severance. Pillsbury declined to discuss layoff decisions beyond its statement.

Many firms are conducting layoffs in this recession, which has caused demand for legal services to plummet. Last week, more than 800 attorneys and staff nationwide were laid off by at least eight major firms. In the last week of January, more than 1,000 people were laid off from law firms.

Last week, Zeughauser said he knew more layoffs were coming, a piece of information he repeated on Thursday, though he declined to name firms.

“I know there are more layoffs coming, big ones,” he said. “And I’m not going to talk about them on the Amtrak train or to a reporter.”

The Layoff List